The invention relates to an assembly for attaching a brake cam shaft to a slack adjuster.
Vehicle brakes in relation to which the present invention may be used usually comprise a brake drum, two opposed brake shoes either pivotally secured at one end to each other or to a brake spider and a cam shaft having a cam member or element at one end and a spline coupling at the other end. The cam element is operative to engage brake rollers secured to the other ends of the shoes and these other ends are normally biassed towards each other and against the cam element whereby upon rotation of the cam shaft the rollers are caused to ride over the cam element to thereby expand the shoes and bring them into contact with the brake drum to effect a braking action. In vehicles and in particular in heavy vehicles the cam shaft is rotated by a slack adjuster which is mounted relative to the splined end of the shaft and itself has a complementary splined aperture. Pivotal movement is achieved by securing the distal end of the slack adjuster to a piston rod of an air chamber via a clevis member. Pressurization of the air chamber causes the piston rod to extend from the chamber and this piston rod is coupled to the clevis member. This extension or stroke of the piston rod pivots the slack adjuster and in turn rotates the cam shaft. The purpose of slack adjusters is well known. Such slack adjusters are designed and used to remove any slack from the brake caused by wear of the brake shoes.
Traditionally, the splined end of the cam shaft was formed with a groove for receiving a circlip. The circlip receiving groove was located adjacent the end of the shaft at which the spline was formed. The shaft was assembled and positioned relative to the slack adjuster by engaging the spline of the shaft with the internal spline of the slack adjuster. Upon engagement and proper positioning of the cam elements of the shaft the circlip was then positioned relative to the shaft. The circlip served only to inhibit longitudinal movement of the shaft in one direction, that is, away from the cam elements. Relative movement of the shaft and slack adjuster was otherwise possible in the longitudinal direction whilst the splines were in engagement. The extent of the movement depended upon play between the clevis member and the distal end of the slack adjuster as well as on any clearance between these two splines. If the freedom of movement of the cam shaft was excessive then this led to undue wear of the spline and in some instances damage to the vehicle brake and possibly to the axles about which the brake drums were mounted. In addition, this circlip type connection tended to damage the side plate of the slack adjuster.